The invention relates to a method for determining a force, and an apparatus to determine the force.
It is known from the related art to couple a car door of an elevator with a pinion gear of a motor shaft of an electric motor so that the car door can be opened and closed by the electric motor. The electric motor is electrically coupled to a power amplifier which is coupled by way of a connecting electrical circuit to an electricity supply unit in the form of a power supply.
Various methods for determining the force of the electric motor acting on the car door are known, for example measuring the motor current and determining the force by the motor constant and the laws of mechanical force transmission. Furthermore, force measuring devices are also possible. Moreover, it is also possible, if the door mass is known, to calculate the force by determining the door's acceleration.
To limit the maximum possible force acting on the elevator car door, in order for example to prevent injury to persons in the event of their becoming trapped, use is made of mechanical devices, a slipping clutch for example, which allow only transmission of a predefined maximum force.
JP 2000128465 A discloses a controller for a door of an elevator, wherein a drive force acting on the door is determined.
It is furthermore possible to limit the force by limiting the motor voltage with a compensation of the counter-electromotive force.